CVE-2014-7923 in Chrome
Summary
by MITRE
The Regular Expressions package in International Components for Unicode (ICU) 52 before SVN revision 292944, as used in Google Chrome before 40.0.2214.91, allows remote attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact via vectors related to a look-behind expression.
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Analysis
by VulDB Data Team • 03/05/2022
The vulnerability identified as CVE-2014-7923 affects the International Components for Unicode (ICU) library version 52 and earlier, specifically impacting Google Chrome versions before 40.0.2214.91. This issue resides within the Regular Expressions package of ICU, which serves as a fundamental component for internationalization and text processing in numerous software applications. The vulnerability manifests through improper handling of look-behind expressions in regular expressions, creating a critical security flaw that can be exploited remotely by attackers.
The technical flaw stems from inadequate validation and memory management within ICU's regular expression engine when processing look-behind patterns. Look-behind expressions are a specific type of regular expression construct that matches a pattern only if it is preceded by another pattern, and they require special handling in the regex engine. When malformed or specially crafted look-behind expressions are processed, the ICU library fails to properly validate the input parameters, leading to memory corruption issues that can result in arbitrary code execution or system crashes. This vulnerability is classified under CWE-129 as "Improper Validation of Array Index" and represents a classic example of how complex string processing functions can become attack vectors when proper bounds checking is absent.
The operational impact of this vulnerability extends far beyond the immediate Chrome browser, as ICU is widely used across various software platforms, operating systems, and applications that require international text processing capabilities. Attackers can exploit this vulnerability by crafting malicious web pages or content that triggers the vulnerable regular expression parsing code, potentially leading to complete system compromise. The memory corruption aspect creates opportunities for attackers to execute arbitrary code, while the denial of service component can be used to disrupt services or applications that rely on ICU for text processing. This vulnerability demonstrates the critical importance of proper input validation in text processing libraries and highlights how seemingly benign functionality can become a serious security risk when not properly secured.
Mitigation strategies for CVE-2014-7923 involve immediate updates to the ICU library to versions that contain proper bounds checking and memory validation for look-behind expressions. Organizations should prioritize updating Google Chrome to version 40.0.2214.91 or later, as well as ensuring that any applications using ICU libraries are updated to versions that address this vulnerability. Network administrators should consider implementing web application firewalls and content filtering mechanisms to block suspicious regular expression patterns. Additionally, developers should adopt defensive programming practices such as input validation, bounds checking, and proper error handling when working with regular expression engines, particularly those that support look-behind constructs. The vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" as attackers may leverage this vulnerability through JavaScript-based web exploits, and represents a classic case of how library-level vulnerabilities can cascade across multiple applications and systems.